The invention is based on a hydraulic brake system with an antilock mechanism especially for motor vehicles as defined hereinafter. German patent application P 40 36 940.4 (U.S. Pat. No. 5,125,721) has already proposed a brake system for a motor vehicle that has a pulsed magnet valve which is closed when without current disposed in a brake line branch associated with at least one rear wheel brake cylinder. A pressure control device with a check valve is disposed parallel to the pulsed magnet valve in a bypass, and this device upon a failure of the antilock mechanism, makes possible a reduced pressure rise in the rear wheel brake cylinders. The pulsed opening of the magnet valve for example associated with both of the rear wheel brake cylinders of the brake system makes possible a reduced pressure rise in the rear wheel brake cylinders and so avoids locking of the rear wheels before locking of the front wheels of the vehicle. However, this brake system has the disadvantage of a comparatively complicated design and high expenditure for controlling the pulsed opening of the magnet valve or valves associated with the rear wheel brake line branches. Moreover, due to the pulsed opening of the magnet valve, sacrifices in comfort arise in the form of an increased generation of noise.